<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>
        // 暂时性死区
        /*{
            console.log(a); /!*报错*!/
            let a=2;
            console.log(a);
        }*/
        // 不能重复定义
        {
            /*报错*/
            let b=1;
            let b=2;
        }
    </script>
</body>
</html>